1. Field of the Invention
The present invention relates to an electrical junction box which is used for wiring arrangement in a motor vehicle or the like, and more particularly to the electrical junction box having a double-wall structure in which deformation of outer walls can be prevented and invasion of water can be restrained.
2. Description of the Related Art
There have been employed in motor vehicles electrical junction boxes such as a junction box, fuse box, relay box, etc. in order to contain various parts required for connecting and treating wire harnesses in the vehicle, and electrical components such as fuses, relays, electronic control unit, etc.
Various types of the electrical junction boxes have been employed according to types of the vehicles. For example, various types of electrical components are contained in a box-like case made of synthetic resin or the like, which is composed of a case body and an upper cover.
Because the electrical junction box is generally arranged at side areas in a lower part of a vehicle body, there is such anxiety that components such as circuits may cause a short circuit or a leaked current may flow, when water has intruded into an interior while driving in rain or at car wash. Therefore, it is necessary to render the electrical junction box waterproof. In case of washing a large car especially, high pressure water jetted with force is liable to intrude into the electrical junction box.
Specifically, the water which has collided against a side wall of the case body will sometimes flow along the side wall, enter between the side wall and the upper cover, and intrude into the case body. For this reason, it has been proposed that the side wall of the case body is formed to have a double-wall structure consisting of an outer wall and an inner wall. According to this structure, even though the water which has collided against the side wall has flowed along the side wall, and entered between the side wall and the upper cover, the water will intrude between the double walls, that is, between the outer wall and the inner wall. This water intruded between the double walls will lose force, and intrusion of the water into the case body can be restrained.
In the above described electrical junction box, the outer wall is held by the inner wall by means of some fixation members at several upper and lower positions between the outer wall and the inner wall, for example. However, since the high pressure water is splashed to the electrical junction box, the outer wall may sometimes be deformed because they are fixed only by means of such fixation means. Moreover, there is formed an opening in a lower part between the outer wall and the inner wall to drain water. When the high pressure water is splashed to this opening, the water may intrude from the opening into a gap between the outer wall and the inner wall, and may arrive at a position between the inner wall and the upper cover. In such cases, there is an anxiety that the water may intrude into the case body.
The present invention has been made in view of such circumstances, and an object of the invention is to provide an electrical junction box having a double-wall structure in which deformation of outer walls can be prevented and invasion of water can be restrained.
In order to attain the above described object, there is provided according to the present invention, an electrical junction box having a double-wall structure comprising a container body and an upper cover to be mounted on the container body, a peripheral wall of the container body including an outer wall and an inner wall, wherein a horizontal rib is provided between the outer wall and the inner wall for partitioning a space between the outer wall and the inner wall into an upper space and a lower space, a plurality of upper ribs and a plurality of lower ribs extending in a vertical direction are respectively provided at a determined interval above and below the horizontal rib, and the horizontal rib is provided with communicating holes, between respective pairs of the upper ribs, which communicate the upper space with the lower space.
With such a structure, the outer wall can be held without deformation, because the outer wall is supported by means of the horizontal rib and a plurality of the upper and lower ribs which are provided above and below the horizontal rib. Moreover, since the horizontal rib is formed between the outer wall and the inner wall, even though high pressurized water has entered into a gap between the outer wall and the inner wall through an opening between them, a large amount of the water will be blocked by the horizontal rib, and invasion of the water into the container body can be restrained.
It is preferable that the upper ribs and the lower ribs are provided substantially in a vertical direction.
This means that the container body, particularly the outer wall, the inner wall, the horizontal, the upper and the lower ribs can be integrally molded by injection molding, for example. Therefore, deformation of the outer wall can be reliably prevented, and a mass production can be attained easily, thus enhancing industrial values.
The horizontal rib is preferably arranged between the outer wall and the inner wall substantially in a middle part in a vertical direction, and each of the lower ribs is preferably arranged substantially in a middle part of a pair of the upper ribs in a horizontal direction.
In this manner, it will be possible to more reliably prevent deformation of the outer wall, because the horizontal rib is arranged substantially in the middle part between the outer wall and the inner wall, and each of the lower ribs is arranged substantially in the middle part between a pair of the upper ribs.
Each of the communicating holes is preferably arranged substantially in a middle part between a pair of the lower ribs.
Because each of the communicating holes is provided substantially in the middle part between a pair of the lower ribs, the water which has intruded from the opening formed in the lower part between the outer wall and the inner wall will collide against the lower ribs and flow along the lower ribs. Since the water will be blocked by the horizontal rib and will not easily intrude into the upper space through the communicating holes, invasion of the water into the container body can be more reliably prevented.
The lower rib is preferably formed in an inverted convex shape having a wider width in its upper part than in its lower part.
In this manner, even though the water flows along the lower ribs, the water will collide against the wider part, and so, invasion of the water into the upper space through the communicating holes will be all the more difficult.
Both lower end portions of the wider part are preferably tapered downwardly toward both ends.
In this manner, the water which has flowed along the lower rib and collided against the wider part will flow along the lower ends to be guided downwardly, and invasion of the water into the upper space through the communicating holes will be all the more difficult.